Onchocerciasis & Filariasis PDF

Onchocerciasis (River blindness)/ Filariasis by D.Afkar Awad Morgan MBBS-MPH-MD Onchocerciasis (River Blindness) by D.Afkar Awad Morgan MBBS-MPH-MD  Objectives of lecture : - Definition Epidemiology -lifecycle -clinical picture Prevention and control...

Onchocerciasis (River blindness)/ Filariasis by D.Afkar Awad Morgan MBBS-MPH-MD Onchocerciasis (River Blindness) by D.Afkar Awad Morgan MBBS-MPH-MD  Objectives of lecture : - Definition Epidemiology -lifecycle -clinical picture Prevention and control  Onchocerciasis is a chronic parasitic disease caused by the filarial worm, Onchocerca volvulus (Nematode) It is the one cause of blindness in the word is transmitted through the bites of infected female black flies of the genus Simulium. In the human body, the larvae mature to adult worms in the subcutaneous tissue, forming subcutaneous nodules. Onchocerca volvulus can live for up to 15 years in the human body.  Epidemiology : It is endemic in 36 countries across Africa, Latin America(brazil-colombia discovered in 1965, ecuador,mexico,venezola,gutemella)has been eliminated in those countries by community -based ivermectine administration program.. called River Blindness because the transmission is most intense in remote rural agricultural villages. It is found near rivers where the rapid flow provides well oxygenated water necessary for development of Simulium. This obligatory aquatic stage of development lasts about 10 days.  The adult flies of some species stay relatively localized while others can travel long distances. Deforestation in Africa is altering the ecosystem in many Simulium habitats, thus the vector distribution is changing The people at risk are those who live or work streams or rivers.most of the areas where the black flies are found are rura agricultural in sub-Saharan Africa. Globally it is estimated that there are 18 million people infected and 270.000 blinded by onchocercasis  The female worm discharges microfilariae that migrate through the skin, often causing an intense pruritic rash when they die, with chronic dermatitis-altered pigmentation, edema and atrophy of the skin, loss of skin elasticity and lymphadenitis. Pigment changes, particularly of the lower limbs, give the condition known as leopard skin.  The worms spread throughout the body, when die, they cause a variety of conditions, including intense itching, a strong immune system response that can destroy nearby tissue, and lead to skin depigmentation. Onchocerciasis is the world’s second leading infectious cause of blindness.  Microfilariae frequently reach the eye, where their invasion and subsequent death causes visual disturbance and blindness, in heavy infections they may also be found in blood, tears, sputum and urine.  According to WHO, Onchocerciasis has not caused a single death but the microfilariae cause a range of debilitating symptoms including blindness( as frequently microfilariae reach the eye ) , lymphadenitis, and chronic dermatitis. Infection also reduces the host’s immunity and resistance to other diseases. Life cycle  The life cycle of O. volvulus: The microfilariae found in the dermis of the infected host, are ingested by female black fly when takes a blood meal. When black fly bites a new non infected host, larvae pass from the fly into his blood. the larvae migrate to the subcutaneous tissue of the host where they form nodules and mature into adult worms over a period of 6-12 months. Humans are the only definitive host for O. volvulus. The normal microfilariae lifespan is 1–2 years. Adult females produce between 1,000 - 3,000 microfilariae per day.  Mode of transmission Only through the bite of infected female blackflies of the genus Simulium Microfilariae, ingested by a blackfly feeding on an infected person, penetrate thoracic muscles of the fly, develop into infective larvae, migrate to the cephalic capsule, are liberated on the skin and enter the bite wound during a subsequent blood-meal.  Transmission: is transmitted from person to person by an infectious black fly black fly needs to inject at least 1-2 larvae to transmit the disease to another person. Simulium flies are day time feeders  Incubation period Microfilariae are found in the skin usually only after 1 year or more from the time of the infective bite Period of communicability—People can infect flies as long as living microfilariae occur in their skin, i.e. for 10–15 years after last exposure to Simulium bites if untreated.  Diagnosis:1- Palpating of subcutaneous nodules. 2-Skin Snips: a tiny slice (3-5 mg) of the skin to observe the microfilariae 3-A microscope with a light is used to examine the eye for free floating intraocular microfilaria 4-Mazzotti Test: If the skin snip is negative, an oral test dose of 5 mg DEC (diethylcarbamazine citrate) is administered. If the patient has onchocerciasis, intense pruritis results within 2 hours due to dying microfilariae. Severe systemic reactions and ocular complications are risks with this diagnostic method. 5-DEC Patch Test: A local application of 10% DEC is applied to the skin and covered with a dressing. The patch is then checked for local dermatitis caused by the dying microfilariae. There is no risk of provoking a systemic reaction, but is not as sensitive as a skin snip. The easy application and low risk of this test make it ideal for testing for the re-emergence of the disease in a treatment area  Treatment: 1-The primary treatment is a Ivermectin drug; the only microfilaricide. Infected people can be treated once every 12 months. For best effect, entire communities are treated at the same time. A single dose may kill microfilariae and prevent transmission for many months in the remaining population. 2-Doxacycline can be added to the treatment regimen; to lower microfilarial loads in the host and may have activity against the adult worms. 3-Suramin: It is the only drug available that is effective in killing the adult worms. Due to side effects, a test dose of 100-200 mg is usually given. Suramin has largely been replaced by Ivermectin in onchocerciasis treatment. 4-DEC (diethylcarbamazine citrate): was used before the invention of Ivermectin  The Onchocerciasis Control Program OCP (WHO): 1-The primary goal of the OCP: is the elimination of onchocerciasis as a public health problem and as an obstacle to socioeconomic development by eliminating the parasite reservoir & so disrupting the transmission of the disease. 2- to use helicopters to aerially apply larvicide into the rivers and nearby breeding habitats of the fly. (This vector control is not effective at eliminating transmission.) 3-To reduce the chance of infection (Black flies bite during the day), is to avoid infective bites of the black fly by:  a- Using insecticides such as DEET, b- Wearing long sleeve shirts and pants, c- avoiding the black fly habitat, d- using insect net. These methods have been found to be less effective for people who live in endemic areas. 4-Ivermectin is available as mass treatment in most areas. 5- No vaccine or effective chemoprophylaxis is available to prevent Onchocerciasis  Lymphatic Filariasis Infection with 3 closely related Nematodes Wuchereria bancrofti Brugia malayi Brugia timori * Transmitted by the bite of infected mosquito responsible for considerable sufferings/deformity and disability * All the parasites have similar life cycle in man * Adults seen in Lymphatic vessels * Offsprings seen in peripheral blood during night  Disease Manifestation Disease manifestation range from None Acute-Filarial fever Chronic-Lymphangitis, Lymphadenitis, Elephantiasis of genitals/legs/arms Tropical Pulmonary Eosinophilia (TPE) Filarial arthritis Epididimoorchitis Chyluria, etc. Lymphatic Filariasis Endemic Countries & Territories Endemic Countries Global Distribution  Agent Factors S.no Parasite Mosquito Disease 1. W.bancrofti Culex LF 2. B.malayi Mansonia LF Anopheles/ 3. B.timori LF Mansonia Simulium River 4. O.volvulus flies Blindness 5. L.loa Chrysops flies S/c swellings 6. M.perstans Culicoides Serous cavity 7. M.streptocerca Culicoides ” 8. M.ozzardi Culicoides ”  VECTORS ANOPHELES AEDES CULEX SIMULIUM CHRYSOPS  Host Factors Man – Natural Host Age – All age (6 months) Max: 20-30 years Sex – Higher in men Migration – leading to extension of infection to non-endemic areas Immunity – may develop after long year of exposure (Basis of immunity-not known)  Social & Environmental Factors Associated with Urbanization, Poverty, Industrialization, Illiteracy and Poor sanitation. Climate: is an important factor which influences: 1. The breeding of mosquito 2. Longevity (Optimum temperature 20-300C & Humidity 70%) 3. The development of parasite in the vector 4. Sanitation, Town planning, Sewage & Drainage.  Mode of Transmission & Incubation Period Lymphatic Filariasis is transmitted by the bite of Infected mosquito which harbours L3 larva. L1: 1-3 hours L2: 3-4 days L3: 5-6 days Pre-patent period: (L3 to Mf) Not known Clinical Incubation period: 8-16 months  Lymphatic Filariasis Clinical Manifestations  Clinical Manifestations Manifestations are 2 types 1. Lymphatic Filariasis (Presence of Adult worms) 2. Occult Filariasis (Immuno hyper responsiveness) Clinical Spectrum Non Asymptomati Filarial Chronic TPE e c fever patholog microfilaremi y  Stages in Lymphatic Filariasis There are 4 stages : 1. Asymptomatic amicrofilariaemic stage 2. Asymptomatic microfilariaemic stage 3. Stage of Acute manifestation 4. Stage of Obstructive (Chronic) lesions  Stage of Asymptomatic amicrofilaraemic In endemic areas, a proportion of population does not show mf or clinical manifestation even though they have some degree of exposure to infective larva similar to those who become infected. Laboratory diagnostic techniques are not able to determine whether they are infected or free.  Stage of Asymptomatic Microfilariaemic Considerable proportions are asymptomatic for months and years, though they have circulating microfilariae. They are an important source of infection. They can be detected by Night Blood Survey and other suitable procedures.  Stage of Acute Manifestation During initial months and years, there are recurrent episodes of Acute inflammation in the lymph vessel/node of the limb & scrotum that are related to bacterial & fungal super infections of the tissue that are already compromised lymphatic function. Clinical manifestations are consisting of: 1. Filarial fever (ADL-DLA) 2. Lymphangitis 3. Lymphadinitis 4. Epididimo orchitis  Chronic Manifestation Chronic (Obstructive) lesions takes 10-15 years. This is due to the permanent damage to the lymph vessels caused by the adult worms, the pathological changes causing dilation of the lymph vessels due to recurrent inflammatory episodes leading to endothelial proliferation and inflammatory granulomnatous reaction around the parasite. Initially, it starts with pitting oedema which gives rise to browny oedema leading to hardening he tissues. Still late, hyper pigmentation, caratosis, wart like lesions are developed. Eg. Hydrocele (40-60%), Elephantiasis of Scrotum, Penis, Leg, Arm, Vulva, Breast, Chyluria.  2. Occult Filariasis (TPE) Occult or Cryptic filariasis, in classical clinical manifestation mf will be absent. Occult filariasis is believed to be the result of hyper responsiveness to filarial antigens derived from mf. Seen more in males. Patients present with paroxysmal cough and wheezing, low grade fever, sputum with occasional haemoptysis, adenopathy and increased eosinophilia. X-ray shows diffused nodular mottling and interstial thickening. Leg Chyluria & Haematuria Arm  Classification of Lymphoedema Lymphoedema is classified into 7 stages on the basis of the presence & absence of the following: 1. Oedema 2. Folds 3. Knobs 4. Mossy foot 5. Disability Stages of Lymphoedema of the Leg (Stage I) Swelling reverses at night Skin folds-Absent Appearance of Skin- Smooth, Normal Stages of Lymphoedema of the Leg (Stage II) Swelling not reversible at night Skin folds-Absent Appearance of skin- Smooth, Normal Stages of Lymphoedema of the Leg (Stage III) Swelling not reversible at night Skin folds-Shallow Appearance of skin- Smooth, Normal Stages of Lymphoedema of the Leg (Stage IV) Swelling not reversible at night Skin folds-Shallow Appearance of skin - Irregular, * Knobs, Nodules  Laboratory Diagnosis 1. Demonstration of microfilarae in the peripheral blood a. Thick blood smear: 2-3 drops of free flowing blood by finger prick method, stained with JSB-II b. Membrane filtration method: 1-2 ml intravenous blood filtered through 3µm pore size membrane filter c. DEC provocative test (2mg/Kg): After consuming DEC, mf enters into the peripheral blood in day time within 30 - 45 minutes. 2. Immuno Chromatographic Test (ICT): Antigen detection assay can be done by Card test and through ELISA. Circulating Filarial Antigen detection is regarded as “Gold Standard” for diagnosing Wuchereria bancrofti infection. Specificity is near complete, sensitivity is greater than all other parasite detection assays, will detect antigen in amicrofilaraemic as well as with clinical manifestations like lymphoedema, elephantiasis.  Twin Pillars of Lymphatic Filariasis Elimination Interrupt transmission Control Morbidity (relief of suffering) # Community-level care of those with disease Lymphoedema Acute inflammatory attacks Hydrocele repair  Lymphatic Filariasis Control Programme The current strategy of filariasis control (Elimination) is based on: 1. Interruption of transmission 2. Control of Morbidity Interruption of the transmission can be achieved through: a. Chemotherapy b. Vector control An integrated programme is in place for the control of lymphatic filariasis. Earlier, vector control was the main method of control. )  Management of Lymphatic Filariasis 1. Treating the infection 2. Treatment and prevention of Acute ADL attacks 3. Treatment and prevention of Lymphoedema  Chemotherapy of Filariasis Drugs effective against filarial parasites 1. Diethyl Carbomazine citrate (DEC) 2. Ivermectin 3. Albendazole 4. Couramin compound Treatment of microfilaraemic patients may prevent chronic obstructive disease and may be repeated every 6 months till mf and/or symptoms disappears.  Thanks